Diagnosing Plant Problems
Neil Bell, OSU Extension Service, Marion and Polk Counties
1320 Capitol Street NE #110, Salem, OR 97301
[email protected]
Plant identification resources
 OSU plant identification website: http://oregonstate.edu/dept/ldplants/
Questions to ask in diagnosing problems
1. Does a “real” problem exist with the plant?
2. What is the “population” of the plants?
3. How many of the plants are affected?
4. What is the pattern of damage in the population? Do the cultural conditions of the
affected plants differ from those of the unaffected plants?
5. What part or parts of the plant is (are) affected?
6. What is the pattern of damage within the plant?
7. What is the pattern of damage on the plant part?
8. When did the symptoms appear?
9. Are the symptoms spreading, improving or constant?
10. Are there any signs of a pest present?
Website list
OSU Extension

OSU Extension Publications: https://catalog.extension.oregonstate.edu/. OSU gardening publications.

Scholars Archive:. http://ir.library.oregonstate.edu/xmlui/ Many gardening publications otherwise
unavailable on the Extension Publications website have migrated here.

OSU Extension Gardening: http://extension.oregonstate.edu/gardening/. Archive of helpful articles!
Plant Diseases

Pacific Northwest Plant Disease Management Handbook: http://pnwhandbooks.org/plantdisease/
Insect Pests

Pacific Northwest Insect Management Handbook: http://insect.pnwhandbooks.org/

Spotted Wing Drosophila information: http://spottedwing.org/

PNW defoliators-What’s eating my plants (WSU): http://invasives.wsu.edu/defoliators/identify.html

Key Gray insect image collection: http://www.ipmnet.org/kgphoto/

WSU Crane fly pests of the PNW: http://whatcom.wsu.edu/cranefly/
Weeds

Pacific Northwest Weed Management Handbook: http://pnwhandbooks.org/weed/
General pest or IPM sites:

University of California Integrated Pest Management: http://www.ipm.ucdavis.edu/index.html

Washington State University Hortsense: http://hortsense.cahnrs.wsu.edu/Home/HortsenseHome.aspx

WSU Pest and Disease Identification leaflets: http://puyallup.wsu.edu/plantclinic/pls/

Pacific Northwest Nursery IPM: http://oregonstate.edu/dept/nurspest/index.htm

USDA Forest service Pacific Region Forest Health Protection:
http://www.fs.usda.gov/detail/r6/forest-grasslandhealth/insects-diseases/?cid=stelprdb5300513